1.反转字符串

    public void reverseString(char[] s) {
    	int len = s.length;
    	int i;
    	for (i = 0; i < len / 2; i++ ) {
    		char temp = s[i];
    		s[i] = s[len-i-1];
    		s[len-i-1] = temp;
    	}
    }